| 摘要 |
PURPOSE:To improve the transient characteristic of an AGC amplifier at an ON/OFF time, by providing a capacitor for AGC and an amplifier high output impedance to charge or discharge the capacitor for AGC so that the gain of an amplifier circuit can be converged to an arbitrary preset gain at the time of turning OFF the function of the AGC. CONSTITUTION:To the capacitor for AGC, a charging/discharging amplifier 8 at the time of holding a gain is connected. And the output impedance of the amplifier 8 is set at a very high level, and it is set at a large value possible to neglect the output impedance of a detection circuit 4 at the time of turning ON a switch 6. In such a way, no effect is given on the operation of the AGC at the time of turning ON it, and also, the voltage of the capacitor is converged so as to be set equal to a reference voltage 7 at the time of turning OFF the switch 6 by providing the amplifier 8. Therefore, it is possible to reduce the fluctuation of the gain of the AGC amplifier at the time of switching the AGC from an OFF state to an ON state. Also, it is possible to set the output of the AGC amplifier constant immediately at the time of switching the AGC from the ON state to the OFF state.
|
